////Main.swift

import Foundation

var anInstanceOfClassA: ClassA = ClassA()
anInstanceOfClassA.initVariable(200)
print(anInstanceOfClassA)
anInstanceOfClassA.showTheValueOfX()

var anInstanceOfClassB: ClassB = ClassB()
anInstanceOfClassB.initVariable(100)
print(anInstanceOfClassB)
anInstanceOfClassB.showTheValueOfX()


///===============================================================
////ClassA.swift

import Foundation

class ClassA: CustomStringConvertible {
    
    var x: Int = 100
    var description: String {return "ClassA x \(x) "}
    
    init()
    {
    }
    
    func initVariable(x: Int) {
       self.x = x
    }
    
    func showTheValueOfX() {
        print("The value of x is \(x)")
    }
    
}

///===============================================================
////ClassB.swift

import Foundation

class ClassB: ClassA {
    
    override var description: String {return "ClassB x \(x) "}
    
    override func showTheValueOfX() {
        print("I am showing the value of x is \(x)")
    }

}